In the past decade optical communications has become an integral technology component for information systems. As semiconductor technology and advanced computing architectures have resulted in processors that operate at frequencies in multiples of GHz, electrical interconnects have become performance bottlenecks.
In 1998, researchers at Bell Labs transmitted 100 simultaneous optical signals using dense wave-division multiplexing over a distance of 400 km, each signal transmitted at a rate of 10 Gbps (gigabits per second). Therefore, optical interconnects show great promise in meeting the ever increasing demand for high speed communications.
The physical layer of an optical communication system may include a transmitter and a receiver, which communicate through an optical pipe such as an optical fiber or a wave guide. The optical transmitter may typically include a light emitter, circuitry to drive or modulate optical signals through the light emitter in response to electronic signals, a clock, and circuitry to convert and/or to encode data into a sequence of electronic signals. The optical receiver may typically include a light detector, circuitry to amplify the output of the light detector, clock recovery circuitry, and circuitry to sample and/or decode the data from the received signals.
Several characteristics of optical communication systems are critical to design choices. Speed is one of the most important characteristics. The rate at which an optical signal can be modulated and the transmitted data can be recovered, may determine, for example, the type of light emitter used, the design of the circuitry to drive or modulate the optical signals through the light emitter and/or the circuitry to amplify the output of the light detector and sample received signals. If an optical communication system is to be suitable to present and future processors operating at frequencies in multiples of GHz, it must be scalable at least to data rates of multiple Gbps.
Cost is another important characteristic of an optical communication system to be used as a component in information systems. If the optical components are not available in cost competitive technologies that are compatible with other components of the information system, they provide little advantage over duplication of existing electrical interconnects.
Reliability of the optical communication system in a variety of operating conditions and accounting for various manufacturing process variations is yet another important characteristic. The optical communication system must be reliable even if components of one manufacturing process are connected to components of another manufacturing process and these components must continue to be reliable, for example, in conditions of great heat or cold.
Such considerations have not been sufficiently addressed in prior art optical communication systems.